A synthetic resin folding container described in Japanese Patent Application Laid-Open No. 3-148451 (reference document 1) is structured such that a container's main body can be folded in an empty state, a male screw is provided in an opening portion of the container's main body, and a cap is mounted to the male screw. Accordingly, even if the container's main body is folded, it is impossible to obtain a folded state in which the entire main body of the container is formed approximately in a flat shape, due to the existence of the opening portion with the male screw and the existence of the cap, such that storing such container in a flat position is difficult.
On the contrary, a self-supporting bag described in Japanese Patent No. 3077751 (reference document 2) is structured such that the bag's main body is formed by laminating synthetic resin front and back body portion sheets and a synthetic resin bottom portion sheet, so that the entire main body of the bag can be folded.